1. Phylum
    2. 1. Classification of Animals
    2. Protozoa
    3. Porifera
    4. Coelenterata
    5. Platyhelminthes
    6. Nemathelminthes
    7. Annelida
    8. Earthworm
    9. Arthropoda
    10. Cockroach
    11. Mosquito
    12. Honey bee and Silk moth
    13. Mollusca
    14. Echinodermata
    15. Hemichordata
    16. Chordata
    17. Pisces
    18. Amphibia
    19. Frog
    20. Reptile
    21. Aves
    22. Mammalia
    23. Rabbit bone
  2. Animal Behaviour and Adaptation
    3. 24. Animal behaviour
    25. Animal adaptation
    26. Migration
  3. Developmental Biology
    4. 27. Development of Animals
    28. Development of Frog
  4. Human Biology
    5. 29. Tissues
    30. Sense organs
    31. Digestive system
    32. Circulatory system
    33. Respiratory system
    34. Nervous system
    35. Endocrine system
    36. Reproductive system
    37. Excretory system
    38. Skeletal system
    39. Basic concept of Immunology
    40. Human diseases
  5. Evolutionary Biology
    6. 41. Origin of Life
    42. Organic Evolution
    43. Theories of Evolution
    44. Evolution of Human beings
    45. Horse Evolution
Phylum
13. Mollusca
▢ Introduction:
❖ Meaning: Term 'Mollusca' means Soft body.
❖ CoinedBy: Term 'Mollusca' was coined by Johnston.
❖ Study:
◉ Malacology: Study of Mollusca is called Malacology.
◉ Conchology: Study of Shells of Mollusca is called Conchology.
❖ Habitat:
◉ Marine: Most members are Marine.
◉ Freshwater: Some are found in Freshwater.
◉ Terrestrial: Few are Terrestrial.
▢ General Characters:
❖ Body Plan:
  1. Triploblastic
  2. Bilateral symmetrical (except Gastropods, which are asymmetrical due to torsion)
  3. Unsegmented body (except Neopilina)
  4. Haemocoelomate
❖ Circulatory System: Open circulatory system (except Sepia, which shows tendency to become closed)
▢ Mantle or Pallial Cavity:
❖ MantleFeatures:
◉ Description: Body covered by a skin fold called mantle with shell glands.
◉ Secretes:
  1. Calcareous spicules
  2. Shell plates
  3. Shells
◉ ShellTypes:
◈ External: Generally external shells
◈ Internal: Sepia, Slug, Loligo
◈ Absent: Octopus
◉ ShellComposition: Shell made up of Calcium carbonate – protects and supports soft tissues.
◉ ShellFeatures:
◈ Umbo: In Unio, the oldest and thickest part of shell is called Umbo.
◈ Layers:
  1. Periostracum
  2. Prismatic layer
  3. Nacreous layer
  4. Mantle
❖ CavityStructures: Mantle cavity contains a pair of pulmonary sacs.
▢ Body Wall:
❖ Epidermis: Single layered ciliated epidermis
▢ Body Regions:
❖ Head: Head bears the mouth and sense organs.
❖ Foot:
◉ Description: Ventral part used for locomotion.
◉ Functions:
  1. Locomotion
  2. Crawling in snails
  3. Modified into tentacles in squid for capturing prey
❖ VisceralHump: Contains digestive tract and other visceral organs.
▢ Digestive System:
❖ Structure:
  1. Complete digestive tract
  2. Digestive gland or liver (hepatopancreas)
❖ BuccalCavity:
◉ Radula:
◈ Description: Rasping organ present in buccal cavity
◈ Structure:
  1. Transverse rows of chitinous teeth
  2. Each row contains 7 teeth
  3. Radula supported by Odontophore (used for straining food)
◈ Example: Present in Pila
◉ Feeding: Cilia of gills in bivalves help in feeding
❖ GreenGland:
◉ Presence: Present in Unio
◉ Function: Analogous to liver of vertebrates
▢ Circulatory System:
❖ Blood:
◉ Contents:
  1. Amoebocytes
  2. Respiratory pigment: Haemocyanin (copper containing, dissolved in plasma)
◉ Color: Blood is blue due to Haemocyanin
▢ Respiratory System:
❖ Organs:
◉ Gills: Aquatic Molluscs (e.g., Monopectinate in Pila)
◉ Pulmonary Sacs: Aerial Molluscs
◉ Direct: Sometimes occurs
▢ Excretory System:
❖ Organs:
  1. Pair of kidneys (Organ of Bojanus)
  2. Pericardial gland (Keber's gland)
▢ Reproductive System:
❖ Type: Sexual reproduction
❖ Sexes: Dioecious or Monoecious
❖ Fertilization: Generally external
❖ Reproduction: Mostly oviparous, few viviparous
❖ Development:
◉ Mode: Direct or via larval forms
◉ Larvae:
  1. Trochophore
  2. Veliger (larva of marine pelecypods)
  3. Glochidium (ectoparasite, metamorphoses in gills of fish)
▢ Nervous System:
❖ Structure:
  1. Paired ganglia
  2. Commissures
  3. Connectives
❖ Type: Complete ladder-like nervous system
❖ Sense Organs:
◉ Eyes: Includes ommatophores (stalks bearing eyes)
◉ Statocysts: Used for maintaining equilibrium
◉ Tentacles: Sensory structures
◉ Osphradia: Chemoreceptors for testing water quality
◉ Lithocysts: Sensory structures
▢ Classification:
S.N.
Aplacophora
Monoplacophora
Polyplacophora
Scaphopoda
Gastropoda
Pelecypoda/ Bivalvia
Cephalopoda/ Siphonopoda
Common name
Solenogasters
Chitons
Tooth shells or Tusk shells
Shell
Absent
Single cap like
8 pieces
Single piece
Single piece, usually spirally coiled.
Bivalve
  1. May be:
  2. • External (Nautilus)
  3. • Internal (Sepia)
  4. • Absent (Octopus)
Foot
Absent
Flat
Muscular
Adapted for digging
Flat, large and highly muscular
Laterally compressed without shell
Located on the head modified in the form of oral arms
Features
1. Calcareous spicules are found.
Most primitive mollusc having characters of Annelids.
During development, Visceral mass and Mantle rotate 90–180° on foot, a phenomenon called Torsion.
Examples
  1. a. Neomenia
  2. b. Chaetoderma
  1. a. Neoplina
  2. • Living fossil and connecting link between annelids and Molluscs
  3. • Segmented body
  1. a. Chiton
  2. b. Lepidopleurus
  1. a. Dentallium (Elephant's Tusk shell)
  1. a. Pila (Apple snail)
  2. b. Helix (Garden snail)
  3. c. Limax (Slug)
  4. d. Turbinella (Shankha)
  5. e. Cypraea (Cowda)
  6. f. Aplysia (Sea hare)
  7. g. Doris (Sea lemon)
  8. 1. Radula is present in it.
  9. 2. Gill is monopectinate.
  10. b. Gill of Pila consists of long ctenidial axis with a single row of a long series of triangular leaflets known as lamellae. Such a gill is called Monopectinate.
  1. a. Unio (Fresh water mussel)
  2. b. Mytilus (Sea water mussel)
  3. c. Teredo (Ship worm)
  4. d. Pecten (Scallops)
  5. e. Pinctada vulgaris (Pearl oyster)
  1. a. Octopus (Devil fish)
  2. b. Sepia (Cuttle fish)
  3. c. Loligo (Squid)
  4. d. Architeuthis (Giant squid)
  5. e. Nautilus
  6. • Closed circulatory system
  7. • Ink gland in some squids for offence and defence.
1. Trocophore larva occurs in

[MOE]

  • Annelida and Porifera
  • Annelida and Mollusca
  • Mollusca and Coelenterata
  • Coelenterata and Annelida
2. Which of the following animal is a mollusca?

[MOE 2000]

  • Silverfish
  • Cuttle fish
  • Flying fish
  • Star fish
3. Which of the following is a cephalopod?

[MOE 2064]

  • Starfish
  • Cuttle fish
  • Silver fish
  • Cray fish
4. Which animal has a modified mantle cavity to expel water with force?

[MOE 2064]

  • Squid
  • Snail
  • Chiton
  • Oyster
5. Which of following is excretory organ in Unio?

[I.E. 2004]

  • Nephridia
  • Flame cells
  • Keber's organ
  • Malphigian organ
6. Ink gland is found in:

[IOM-2014]

  • Octopus
  • Oyster
  • Cuttle fish
  • Hydra
7. Which of the following belongs to mollusca?

[IOM-2013]

  • Cuttle fish
  • Gold fish
  • Silver fish
  • Starfish
8. Pila belongs to

[KU 2013]

  • Arthropoda
  • Coelenterata
  • Mollusca
  • Porifera